Electrosurgical instrument

Abstract

An electrosurgical instrument for delivering microwave energy to biological tissue, in which a pair of conductive tuning elements are mounted in a radiating instrument tip to shape a microwave radiation profile of the instrument so that the radiation profile is constrained around the instrument tip. Such tuning elements may result in a radiation profile that is substantially spherical around the instrument tip, providing a well-defined ablation volume. The tuning elements act to improve the efficiency with which microwave energy can be delivered into target tissue.

The invention claimed is: 
     
       1. An electrosurgical instrument comprising:
 a coaxial feed cable for conveying microwave energy, the coaxial feed cable having an inner conductor, an outer conductor, and a dielectric material separating the inner conductor and the outer conductor; and 
 a radiating tip disposed at a distal end of the coaxial feed cable to receive the microwave energy, the radiating tip comprising:
 an elongate conductor electrically connected to the inner conductor and extending in a longitudinal direction to form a microwave radiator; 
 a proximal tuning element electrically connected to the elongate conductor in a proximal region of the radiating tip; 
 a distal tuning element electrically connected to the elongate conductor in a distal region of the radiating tip; and 
 a dielectric body disposed around the elongate conductor, the proximal tuning element and the distal tuning element; 
 a conductive field shaping element disposed at a distal end of the coaxial feed cable, the conductive field shaping element being electrically connected to the outer conductor along a full length of the conductive field shaping element to increase an effective thickness of the outer conductor; 
 
 wherein the proximal tuning element and the distal tuning element are spaced apart in the longitudinal direction, whereby a microwave field emitted by the microwave radiator is shaped around the dielectric body; and 
 wherein a length of the distal tuning element in the longitudinal direction is greater than a length of the proximal tuning element in longitudinal direction. 
 
     
     
       2. An electrosurgical instrument according to  claim 1 , wherein the proximal tuning element and the distal tuning element are symmetrical with respect to the longitudinal direction. 
     
     
       3. An electrosurgical instrument according to  claim 1 , wherein the proximal tuning element and the distal tuning element are cylindrical, and have a central axis that is collinear with a longitudinal axis of the elongate conductor. 
     
     
       4. An electrosurgical instrument according to  claim 1 , wherein the proximal tuning element is spaced from the distal end of the coaxial feed cable in the longitudinal direction. 
     
     
       5. An electrosurgical instrument according to  claim 4  comprising a dielectric element mounted between the proximal tuning element and a distal end of the coaxial feed cable. 
     
     
       6. An electrosurgical instrument according to  claim 5 , wherein the dielectric element comprises a distal portion of the dielectric material of the coaxial feed cable that protrudes beyond a distal end of the outer conductor. 
     
     
       7. An electrosurgical instrument according to  claim 1 , wherein the proximal tuning element and the distal tuning element each comprise a channel through which the elongate conductor extends. 
     
     
       8. An electrosurgical instrument according to  claim 1 , wherein the distal tuning element is located at a distal end of the elongate conductor. 
     
     
       9. An electrosurgical instrument according to  claim 1 , wherein the elongate conductor is a distal portion of the inner conductor that extends beyond a distal end of the outer conductor. 
     
     
       10. An electrosurgical instrument according to  claim 1 , wherein the dielectric body comprises a dielectric spacer between the proximal tuning element and the distal tuning element. 
     
     
       11. An electrosurgical instrument according to  claim 1 , wherein the dielectric body comprises a dielectric sheath that surrounds an outer surface of the proximal tuning element and the distal tuning element. 
     
     
       12. An electrosurgical instrument according to  claim 11 , wherein an outer surface of the dielectric sheath is flush with an outer surface of the coaxial feed cable at an interface between the coaxial feed cable and the radiating tip. 
     
     
       13. An electrosurgical instrument according to  claim 1 , wherein the radiating tip further includes a distal tip mounted at a distal end of the elongate conductor, the distal tip being made of a dielectric material. 
     
     
       14. An electrosurgical instrument according to  claim 13 , wherein the distal tip is pointed. 
     
     
       15. An electrosurgical instrument according to  claim 1 , wherein the conductive field shaping element is formed by a distal portion of the outer conductor having an increased thickness compared to a proximal portion of the outer conductor. 
     
     
       16. An electrosurgical instrument according to  claim 1 , wherein the conductive field shaping element has a length in the longitudinal direction corresponding to a quarter wavelength of the microwave energy. 
     
     
       17. An electrosurgical apparatus for treating biological tissue, the electrosurgical apparatus comprising:
 an electrosurgical generator arranged to supply microwave energy; and 
 an electrosurgical instrument according to  claim 1  connected to receive the microwave energy from the electrosurgical generator. 
 
     
     
       18. An electrosurgical apparatus according to  claim 17  further comprising a surgical scoping device that comprises a flexible insertion cord having an instrument channel, wherein the electrosurgical instrument is dimensioned to fit within the instrument channel. 
     
     
       19. An electrosurgical instrument comprising:
 a coaxial feed cable for conveying microwave energy, the coaxial feed cable having an inner conductor, an outer conductor, and a dielectric material separating the inner conductor and the outer conductor; and 
 a radiating tip disposed at a distal end of the coaxial feed cable to receive the microwave energy, the radiating tip comprising:
 an elongate conductor electrically connected to the inner conductor and extending in a longitudinal direction to form a microwave radiator; 
 a proximal tuning element electrically connected to the elongate conductor in a proximal region of the radiating tip; 
 a distal tuning element electrically connected to the elongate conductor in a distal region of the radiating tip; and 
 a dielectric body disposed around the elongate conductor, the proximal tuning element and the distal tuning element; 
 wherein the proximal tuning element and the distal tuning element are spaced apart in the longitudinal direction, whereby a microwave field emitted by the microwave radiator is shaped around the dielectric body; and 
 
 wherein a length of the distal tuning element in the longitudinal direction is twice or more than a length of the proximal tuning element in the longitudinal direction.